• Journal of information and communication convergence engineering
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• v.14 no.1
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• pp.35-39
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• 2016

In this paper, we develop a 94-GHz single balanced mixer with low conversion loss using planar Schottky diodes on a GaAs substrate. The GaAs Schottky diode has a nanoscale anode with a T-shaped disk that can yield high cutoff frequency characteristics. The fabricated Schottky diode with an anode diameter of 500 nm has a series resistance of 21 Ω, an ideality factor of 1.32, a junction capacitance of 8.03 fF, and a cutoff frequency of 944 GHz. Based on this technology, a 94-GHz single balanced mixer was constructed. The fabricated mixer shows an average conversion loss of -7.58 dB at an RF frequency of 92.5 GHz to 95 GHz and an IF frequency of 500 MHz with an LO power of 7 dBm. The RF-to-LO isolation characteristics were greater than -32 dB. These values are considered to be attributed to superior Schottky diode characteristics.

• Bulletin of the Korean Space Science Society
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• 2006.04a
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• pp.121-124
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• 2006

B-dot logic is generally used for controlling the initial tip-off rate. However, it has the disadvantage of taking a relatively long time to control the initial tip-off rate. To solve this problem, this paper suggests a new detumbling control method to be able to adapt to micro/nanosatellite with the pitch bias momentum system. Proposed detumbling method was able to control the angular rate within 20 minutes which is a significant reduction compared to conventional methods.

• Journal of Advanced Navigation Technology
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• v.20 no.6
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• pp.631-637
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• 2016

Quantum cellular automata (QCA) are one of the alternative technologies that can overcome the limits of complementary metal-oxide-semiconductor (CMOS) scaling. It consists of nano-scale cells and demands very low power consumption. Various circuits on QCA have been researched until these days, and in the middle of the researches, exclusive-OR (XOR) gates are used as error detection and recover. Typical XOR logic gates have a lack of scalable, many clock zones and crossover designs so that they are difficult to implement. In order to overcome these disadvantages, this paper proposes XOR design using majority gate reduced clock zone. The proposed design is compared and analysed to previous designs and is verified the performance.

• Transactions on Electrical and Electronic Materials
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• v.3 no.3
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• pp.8-13
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• 2002

Controlled precipitation of quasi-binary semiconductor system is newly proposed as an effective and reliable technique for the formation of well-defined and crystallographically aligned semiconductor nanostructures. Using HgTe-PbTe quasi-binary semiconductor system, self-aligned HgTe nanocrystallites distributed three dimensionally within PbTe matrix were successfully formed by the simple three step heat treatment process routinely found in age hardening process of metallic alloys. Examination of the resulting nano precipitates using conventional transmission electron microscopy (CTEM) and high resolution TEM (HRTEM) reveals that the coherent HgTe precipitates form as thin discs along the (100) habit planes making a crystallographic relation of {100}$\_$HgTe///{100}$\_$PbTe/ and [100]$\_$HgTe///[100]$\_$PbTe/. It is also found that the precipitate undergoes a gradual thickening and a faceting under isothermal aging up to 500 hours without any noticeable coarsening. These results, combined with the extreme dimension of the precipitates (4-5 nm in length and sub-nanometer in thickness) and the simplicity of the formation process, leads to the conclusion that controlled precipitation is an effective method for preparing desirable quantum-dot nanostructures.

• Korean Journal of Materials Research
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• v.22 no.3
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• pp.140-144
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• 2012

Compared with bulk material, quantum dots have received increasing attention due to their fascinating physical properties, including optical and electronic properties, which are due to the quantum confinement effect. Especially, Luminescent CdSe quantum dots have been highly investigated due to their tunable size-dependent photoluminescence across the visible spectrum. They are of great interest for technical applications such as light-emitting devices, lasers, and fluorescent labels. In particular, quantum dot-based light-emitting diodes emit high luminance. Quantum dots have very high luminescence properties because of their absorption coefficient and quantum efficiency, which are higher than those of typical dyes. CdSe quantum dots were synthesized as a function of the synthesis time and synthesis temperature. The photoluminescence properties were found strongly to depend on the reaction time and the temperature due to the core size changing. It was also observed that the photoluminescence intensity is decreased with the synthesis time due to the temperature dependence of the band gap. The wavelength of the synthesized quantum dots was about 550-700 nm and the intensity of the photoluminescence increased about 22~70%. After the CdSe quantum dots were synthesized, the particles were found to have grown until reaching a saturated concentration as time increased. Red shift occurred because of the particle growth. The microstructure and phase developments were measured by transmission electron microscopy (TEM) and X-ray diffractometry (XRD), respectively.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.2
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• pp.227-236
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• 2017

Quantum-dot cellular automata(QCA) consists of nano-scale cells and demands very low power consumption so that it is one of the alternative technologies that can overcome the limits of scaling CMOS technologies. Various circuits on QCA have been researched until these days, a latch required for counter and state control has been proposed as a component of sequential logic circuits. A latch uses a feedback loop to maintain previous state. In QCA, a latch uses a square structure using 4 clocks for feedback loop. Previous latches have been proposed using many cells and clocks in coplanar. In this paper, in order to eliminate these defects, we propose a SR and D latch using multilayer structure on QCA. Proposed three dimensional loop structure is based on multilayer and consists of 3 layers. Each layer has 2 clock differences between layers in order to reduce interference. The proposed latches are analyzed and compared to previous designs.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.3
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• pp.291-300
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• 2017

Quantum-dot cellular automata(QCA) is a computing model designed to be similar to cellular automata, and an alternative technology for next generation using high performance and low power consumption. QCA is undergoing various studies with recent experimental results, and it is one of the paradigms of transistors that can solve device density and interconnection problems as nano-unit materials. An XOR gate is a gate that operates so that the result is true when either one of the logic is true. The proposed XOR gate consists of five layers. The first layer consists of OR gates, the third and fifth layers consist of AND gates, and the second and fourth layers are designed as passages in the middle. The half adder consists of an XOR gate and an AND gate. The proposed half adder is designed by adding two cells to the proposed XOR gate. The proposed half adder consists of fewer cells, total area, and clock than the conventional half adder.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.3
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• pp.301-310
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• 2017

Quantum-dot cellular automata(QCA) is an alternative technology for implementing various computation, high performance, and low power consumption digital circuits at nano scale. In this paper, we propose a new universal gate in QCA. By using the universal gate, we propose a novel XOR gate which is reduced time/hardware complexity. The universal gate can be used to construct all other basic logic gates. Meanwhile, the proposed universal gate is designed by basic cells and a rotated cell. The rotated cell of the proposed universal gate is located at the central of 3-input majority gate structure. In this paper, we propose an XOR gate using three universal gates, although more than five 3-input majority gates are used to design an XOR gate using the 3-input majority gate. The proposed XOR gate is superior to the conventional XOR gate in terms of the total area and the consumed clock because the number of gates are reduced.

• Design & Manufacturing
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• v.13 no.4
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• pp.40-44
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• 2019

The light diffusion component spreads the light from one point evenly over a large area. Various types of light diffusion parts such as films and lenses are applied in the high-tech industries such as LCD display devices, lighting devices, and solar energy generation. Among these, a diffuser sheet (Diffuser Sheet) has a function to uniformly distribute the light, and various studies have been conducted to improve its function. The shape of the conventional light diffusion pattern is mainly made of a dot or hemispherical shape. In this study, a rectangular cone-shaped structure having a light diffusion function and an advantage of controlling the angle of refraction of light was fabricated by using a solenoid indentation process. The change in shape of the indentation structure was analyzed.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.201-208
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• 2006

Optical characteristics of InGaAs quantum dot (QD) laser structures with an Al native oxide (AlOx) layer as a current-blocking layer were studied by means of photoluminescence (PL), PL excitation, and spatially-resolved micro-PL techniques. The InGaAs QD samples were first grown by molecular-beam epitaxy (MBE), and then prepared by wet oxidation and thermal annealing techniques. For the InGaAs QD structures treated by the wet oxidation and thermal annealing processes, a broad PL emission due to the intermixing effect of the AlOx layer was observed at PL emission energy higher than that of the non-intermixed region. We observed a dominant InGaAs QD emission at about 1.1 eV in the non-oxide AlAs region, while InGaAs QD-related emissions at about 1.16 eV and $1.18{\sim}1.20eV$ were observed for the AlOx and the SiNx regions, respectively. We conclude that the intermixing effect of the InGaAs QD region under an AlOx layer is stronger than that of the InGaAs QD region under a non-oxided AlAs layer.